Addiction to drugs of abuse is a serious affliction of the human population, leading to enormous governmental expenditures and having negative impacts on the lives of many people. The best accepted animal model for drug abuse is self-administration, in which animals are trained to perform an action that leads to drug administration. Animals will self-administer many drugs of abuse, and the degree of self-administration is a measure of abuse liability. The extent to which an animal will work to obtain drug is a measure of its motivation for the drug, and is a measure of drug craving, an important aspect of the addictive process of humans.
A common means of drug self-administration in animal models is via an indwelling catheter implanted into the jugular, or other vein. This method requires difficult surgery, including anesthesia, and involves some degree of suffering to the animal. While commonly used in primates, and feasible in large rodents such as rats, intravenous drug self-administration is difficult in smaller rodents such as the genetically tractable animal model, the mouse. Although techniques have been described for implantation of intravenous catheters in the mouse, and such methods are used in animal experimentation, their utility is limited, since the catheters cannot be extended into the heart without severe tissue damage. Thus the intravenous catheters become blocked within a period of a few days after implantation, limiting the extent to which an individual animal can be studied.
The present invention is directed to a device and method for non-invasive self-administration that works efficiently in the mouse, and should be applicable to a wide variety of animal models. Since this method does not require surgery, it is easier to establish, and does not suffer the disadvantage of catheter blockade, allowing a full behavioral analysis of self-administration behavior not possible with intravenous administration. Additionally, since people ingest some drugs by inhalation, this method provides a more realistic model for this class of drugs.